1. Field of the Invention
The present invention relates to a bearing, a bearing mechanism, and a plunger pump in which the reliability is raised.
2. Description of the Related Art
Conventionally, a plunger pump which comprises an eccentric cam, a bearing, and a pair of plungers is known. In this plunger pump, the eccentric cam is rotated by a motor. The bearing is arranged on the circumference of the eccentric cam and held on the eccentric cam. The plungers are brought in contact with the eccentric cam during the rotation of the eccentric cam so that the plungers are reciprocated. For example, see Japanese Laid-Open Patent Application No. 06-093964.
In the bearing mechanism of the above-mentioned plunger pump, the oil of the bearing is flown to the side of the outer race side due to the centrifugal force of the eccentric cam, and a negative pressure arises on the inner race side.
With the negative pressure, the air contained in the oil is turned into air bubbles, and the air bubbles appear in the oil. With an increase of the temperature, the volume of the air bubbles in the oil expands.
In such circumstances, the oil film with an appropriate thickness for the bearing is not formed, which may place the bearing in an overheating condition and may cause deterioration of the durability of the bearing.
Moreover, when the above-mentioned conventional plunger pump is carried on a control brake device, the oil with the air-bubbles contained is mixed with the working fluid of the control brake device, which may cause a malfunction of the control brake device to take place.